As displays are utilized more often in automotive applications, the use of touch lenses in front of the display is becoming more prevalent. These touch lenses may either have an air gap between the display and the touch lens, or be optically bonded to the display.
There is also a desire to provide a flush touch lens appearance as demonstrated in many mobile devices currently available. This is superior to a “picture frame” type geometry that has a raised wide border above the surface of the touch surfaces.
FIG. 1(a) illustrates an example of a flush mobile device 100, with a bezel 102 and a touch screen 101. As shown, the bezel 102 and the touch screen 101 are substantially level, thereby providing a smooth interface.
On the contrary, FIG. 1(b) illustrates a mobile device 110, with a raised bezel 112 and a touch screen 111. The device 110 is considered less favorable, as it is considered to be less aesthetically pleasing to an end consumer of the mobile device.
Automotive touch lens applications have regulatory safety requirements depending on the location in the vehicle. In general, in order to achieve a flush appearance and pass automotive head impact testing, such as ECE21 & FMVSS201, most solutions require the use of a plastic substrate lens in order to prevent hazardous glass sharp edge exposure and expulsion. However there is a desire to use a glass front lens for a thinner more rigid structure with superior optical characteristics. It is generally considered very risky to use an exposed glass lens. Although a thin plastic film has be applied to the front surface to contain glass shards under a head impact event, generally there is a problem with sharp edges or detached glass expulsion around the perimeter of the part.